It is well known that normally solid polymers of olefins can be prepared by polymerizing the olefins in a hydrocarbon diluent in a turbulent reaction zone. Such processes are frequently carried out in such a manner as to produce particles of polymer which are substantially insoluble in the diluent. These processes are often referred to as "particle-form" polymerization processes. Such processes have certain economic advantages because it is not necessary to recover polymer from a solvent. This inherently simplifies the polymer recovery procedure. However, it has been found that the polymer particles often tend to adhere to the reactor walls to reduce heat transfer. This adherence of polymer particles may result in the reactor becoming plugged.